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copied!<p>In 64-bit mode you cannot push and pop 32-bit values; you need <code>pushq</code> and <code>popq</code>.</p> <p>Also, you will not get a proper exit this way. On 32-bit x86, you would need to set <code>%eax</code> to 1 to select the <code>exit()</code> system call, <em>and</em> set <code>%ebx</code> to the exit code you actually wish. On 64-bit x86 (that's what you are using), conventions are different: the system call number for <code>exit()</code> is 60, not 1; the first system call parameter goes in <code>%rdi</code>, not <code>%rbx</code>; the system-call invocation opcode is not <code>int $0x80</code> but the special, x86-64-only opcode <code>syscall</code>.</p> <p>Which leads to:</p> <pre><code>.section .data .section .text .globl _start _start: pushq $60 popq %rax pushq $1 popq %rdi syscall </code></pre> <p>(each <code>push</code>/<code>pop</code> sequence can be replaced with a simple <code>mov</code> (like <code>mov $60, %eax</code>) of course; I suppose that you are trying to explicitly test <code>push</code> and <code>pop</code>, optimize for code-size, or avoid <code>0</code> bytes in the machine code (for an exploit payload))</p> <hr> <p>Related: </p> <ul> <li><a href="https://stackoverflow.com/questions/2535989/what-are-the-calling-conventions-for-unix-linux-system-calls-on-x86-64">What are the calling conventions for UNIX & Linux system calls on i386 and x86-64</a></li> <li><a href="https://stackoverflow.com/questions/46087730/what-happens-if-you-use-the-32-bit-int-0x80-linux-abi-in-64-bit-code">What happens if you use the 32-bit int 0x80 Linux ABI in 64-bit code?</a></li> </ul>

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